Combination of dexamethasone and etanercept reduces secondary damage in experimental spinal cord trauma

Selective Inhibition of Soluble Tumor Necrosis Factor Alters the Neuroinflammatory Response following Moderate Spinal Cord Injury in Mice

Clinical and animal model studies have implicated inflammation and glial and peripheral immune cell responses in the pathophysiology of spinal cord injury (SCI). A key player in the inflammatory response after SCI is the pleiotropic cytokine tumor necrosis factor (TNF), which exists both in both a transmembrane (tmTNF) and a soluble (solTNF) form. In the present study, we extend our previous findings of a therapeutic effect of topically blocking solTNF signaling after SCI for three consecutive days on lesion size and functional outcome to study the effect on spatio-temporal changes in the inflammatory response after SCI in mice treated with the selective solTNF inhibitor XPro1595 and compared to saline-treated mice. We found that despite comparable TNF and TNF receptor levels between XPro1595- and saline-treated mice, XPro1595 transiently decreased pro-inflammatory interleukin (IL)-1β and IL-6 levels and increased pro-regenerative IL-10 levels in the acute phase after SCI. This was complemented by a decrease in the number of infiltrated leukocytes (macrophages and neutrophils) in the lesioned area of the spinal cord and an increase in the number of microglia in the peri-lesion area 14 days after SCI, followed by a decrease in microglial activation in the peri-lesion area 21 days after SCI. This translated into increased myelin preservation and improved functional outcomes in XPro1595-treated mice 35 days after SCI. Collectively, our data suggest that selective targeting of solTNF time-dependently modulates the neuroinflammatory response by favoring a pro-regenerative environment in the lesioned spinal cord, leading to improved functional outcomes.

Biomaterial-targeted precision nanoparticle delivery to the injured spinal cord

Drug delivery requires precision in timing, location, and dosage to achieve therapeutic benefits. Challenges in addressing all three of these critical criteria result in poor temporal dexterity, widespread accumulation and off-target effects, and high doses with the potential for toxicity. To address these challenges, we have developed the BiomatErial Accumulating Carriers for On-demand Nanotherapy (BEACON) platform that utilizes an implantable biomaterial to serve as a target for systemically delivered nanoparticles (NPs). With the BEACON system, administered NPs are conjugated with a ligand that has high affinity for a receptor in the implanted biomaterial. To test BEACON, an in vivo spinal cord injury (SCI) model was used as it provides an injury model where the three identified criteria can be tested as it is a dynamic and complicated injury model with no currently approved therapies. Through our work, we have demonstrated temporal dexterity in NP administration by injecting 6 days post-SCI, decreased off-target accumulation with a significant drop in liver accumulation, and retention of our NPs in the target biomaterial. The BEACON system can be applied broadly, beyond the nervous system, to improve systemically delivered NP accumulation at an implanted biomaterial target. STATEMENT OF SIGNIFICANCE: Targeted drug delivery approaches have the potential to improve therapeutic regimens for patients on a case-by-case basis. Improved localization of a therapeutic to site of interest can result in increased efficacy and limit the need for repeat dosing. Unfortunately, targeted strategies can fall short when receptors on cells or tissues are too widespread or change over the course of disease or injury progression. The BEACON system developed herein eliminates the need to target a cell or tissue receptor by targeting an implantable biomaterial with location-controllable accumulation and sustained presentation over time. The targeting paradigm presented by BEACON is widely applicable throughout tissue engineering and regenerative medicine without the need to retool for each new application.

Conditional Ablation of Myeloid TNF Improves Functional Outcome and Decreases Lesion Size after Spinal Cord Injury in Mice

Spinal cord injury (SCI) is a devastating condition consisting of an instant primary mechanical injury followed by a secondary injury that progresses for weeks to months. The cytokine tumor necrosis factor (TNF) plays an important role in the pathophysiology of SCI. We investigated the effect of myeloid TNF ablation (peripheral myeloid cells (macrophages and neutrophils) and microglia) versus central myeloid TNF ablation (microglia) in a SCI contusion model. We show that TNF ablation in macrophages and neutrophils leads to reduced lesion volume and improved functional outcome after SCI. In contrast, TNF ablation in microglia only or TNF deficiency in all cells had no effect. TNF levels tended to be decreased 3 h post-SCI in mice with peripheral myeloid TNF ablation and was significantly decreased 3 days after SCI. Leukocyte and microglia populations and all other cytokines (IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, and IFNγ) and chemokines (CCL2, CCL5, and CXCL1) investigated, in addition to TNFR1 and TNFR2, were comparable between genotypes. Analysis of post-SCI signaling cascades demonstrated that the MAPK kinase SAPK/JNK decreased and neuronal Bcl-XL levels increased post-SCI in mice with ablation of TNF in peripheral myeloid cells. These findings demonstrate that peripheral myeloid cell-derived TNF is pathogenic in SCI.

Effects of dexamethasone on autophagy and apoptosis in acute spinal cord injury

Previous studies have indicated that spinal cord injury can induce autophagy. To a certain extent, increased autophagy has a protective effect on neurons. Early hormone therapy is well recognized as a treatment for spinal cord injury. However, whether the protective effect of autophagy is important in recovery from spinal cord injury remains unclear. In this study, we established an in-vitro model of spinal cord injury to study the effects of dexamethasone on mechanical injury, autophagy, and apoptosis in spinal cord neurons. The results showed that dexamethasone inhibited the level of autophagy in the injured nerve cells in a dose-dependent manner. High doses of dexamethasone protected the damaged spinal cord neurons by inhibiting apoptosis, but a protective effect from low hormone concentrations was not obvious. When autophagy was inhibited in damaged spinal cord neurons, apoptosis decreased significantly; in contrast, impairment of autophagy-induced activation of spinal cord neurons and apoptosis levels were significantly increased.

Locomotor activity of rats with SCI is improved by dexmedetomidine by targeting the expression of inflammatory factors

Dexmedetomidine, a well‑known selective α‑2 adrenoceptor agonist, inhibits the apoptosis of neurons and protects other organs from oxidative damage. In the present study, the effect of dexmedetomidine on spinal cord injury (SCI) in a rat model was investigated. The SCI rat model was prepared using the weight‑drop method, and the effect of dexmedetomidine on locomotor activity was analyzed using the Basso, Beattie and Bresnahan (BBB) rating scale. Western blot analysis was used to observe changes in the expression of apoptosis‑related proteins, including B‑cell lymphoma 2 (Bcl‑2) and Bcl‑2‑associated X protein (Bax). The results revealed that treatment of the SCI rats with dexmedetomidine at a dose of 50 mg/kg significantly prevented the formation of edema in the tissues of the spinal cord. Dexmedetomidine also inhibited the SCI‑induced accumulation of neutrophils in the spinal cord. The BBB scores were significantly increased (P<0.05) in the rats with SCI treated with dexmedetomidine after 10 days. The results of grid walking test revealed a marked decrease in the number of missteps following 10 days of dexmedetomidine treatment. The expression levels of tumor necrosis factor (TNF)‑α and interleukin (IL)‑1β were significantly reduced (P<0.05) in the spinal cord tissues of the dexmedetomidine group, compared with those in the control group of rats. Dexmedetomidine treatment following SCI exerted an inhibitory effect on the SCI‑induced increase in the expression of Bax. The expression of Bcl‑2 was increased in the dexmedetomidine treated rats, compared with that in the control group. Taken together, dexmedetomidine improved the locomotor activity of the rats through the inhibition of edema, reduction in the expression levels of TNF‑α and IL‑1β, and inhibition of the induction of apoptosis. Therefore, dexmedetomidine may be of therapeutic importance for patients with SCI.

Role of Caspase-8 and Fas in Cell Death After Spinal Cord Injury

Spinal cord injury (SCI) causes the death of neurons and glial cells due to the initial mechanical forces (i.e., primary injury) and through a cascade of secondary molecular events (e.g., inflammation or excitotoxicity) that exacerbate cell death. The loss of neurons and glial cells that are not replaced after the injury is one of the main causes of disability after SCI. Evidence accumulated in last decades has shown that the activation of apoptotic mechanisms is one of the factors causing the death of intrinsic spinal cord (SC) cells following SCI. Although this is not as clear for brain descending neurons, some studies have also shown that apoptosis can be activated in the brain following SCI. There are two main apoptotic pathways, the extrinsic and the intrinsic pathways. Activation of caspase-8 is an important step in the initiation of the extrinsic pathway. Studies in rodents have shown that caspase-8 is activated in SC glial cells and neurons and that the Fas receptor plays a key role in its activation following a traumatic SCI. Recent work in the lamprey model of SCI has also shown the retrograde activation of caspase-8 in brain descending neurons following SCI. Here, we review our current knowledge on the role of caspase-8 and the Fas pathway in cell death following SCI. We also provide a perspective for future work on this process, like the importance of studying the possible contribution of Fas/caspase-8 signaling in the degeneration of brain neurons after SCI in mammals.

γδ T cells provide the early source of IFN-γ to aggravate lesions in spinal cord injury

Immune responses and neuroinflammation are critically involved in spinal cord injury (SCI). γδ T cells, a small subset of T cells, regulate the inflammation process in many diseases, yet their function in SCI is still poorly understood. In this paper, we demonstrate that mice deficient in γδ T cells (TCRδ^-/- ) showed improved functional recovery after SCI. γδ T cells are detected at the lesion sites within 24 hours after injury and are predominantly of the Vγ4 subtype and express the inflammatory cytokine IFN-γ. Inactivating IFN-γ signaling in macrophages results in a significantly reduced production of proinflammatory cytokines in the cerebrospinal fluid (CSF) of mice with SCIs and improves functional recovery. Furthermore, treatment of SCI with anti-Vγ4 antibodies has a beneficial effect, similar to that obtained with anti-TNF-α. In SCI patients, γδ T cells are detected in the CSF, and most of them are IFN-γ positive. In conclusion, manipulation of γδ T cell functions may be a potential approach for future SCI treatment.

Dexamethasone Downregulates Endothelin Receptors and Reduces Endothelin-Induced Production of Matrix Metalloproteinases in Cultured Rat Astrocytes

In brain disorders, astrocytes change phenotype to reactive astrocytes and are involved in the induction of neuroinflammation and brain edema. The administration of glucocorticoids (GCs), such as dexamethasone (Dex), reduces astrocytic activation, but the mechanisms underlying this inhibitory action are not well understood. Endothelins (ETs) promote astrocytic activation. Therefore, the effects of Dex on ET receptor expressions were examined in cultured rat astrocytes. Treatment with 300 nM Dex for 6-48 hours reduced the mRNA expression of astrocytic ET_A and ET_B receptors to 30-40% of nontreated cells. Levels of ET_A and ET_B receptor proteins became about 50% of nontreated cells after Dex treatment. Astrocytic ET_A and ET_B receptor mRNAs were decreased by 300 nM hydrocortisone. The effects of Dex and hydrocortisone on astrocytic ET receptors were abolished in the presence of mifepristone, a GC receptor antagonist. Although Dex did not decrease the basal levels of matrix metalloproteinase (MMP) 3 and MMP9 mRNAs, pretreatment with Dex reduced ET-induced increases in MMP mRNAs. The effects of ET-1 on the release of MMP3 and MMP9 proteins were attenuated by pretreatment with Dex. ET-1 stimulated the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in cultured astrocytes. Pretreatment with Dex reduced the ET-induced increases in ERK1/2 phosphorylation. In contrast, pretreatment with Dex did not affect MMP production or ERK1/2 phosphorylation induced by phorbol myristate acetate, a protein kinase C activator. These results indicate that Dex downregulates astrocytic ET receptors and reduces ET-induced MMP production.

Coadministration of Dexamethasone and Melissa officinalis Has Neuroprotective Effects in Rat Animal Model with Spinal Cord Injury

Objective

Spinal cord injury (SCI) causes inflammation, deformity and cell loss. It has been shown that Melissa officinalis (MO), as herbal medicine, and dexamethasone (DEX) are useful in the prevention of various neurological diseases. The present study evaluated combinational effects of DEX and MO on spinal cord injury.

Materials and Methods

Thirty six adult male Wistar rats were used in this experimental study. The weight-drop contusion method was employed to induce spinal cord injury in rats. DEX and MO were administrated alone and together in different treatment groups. Intra-muscular injection of DEX (1 mg/kg) was started three hours after injury and continued once a day for seven days after injury. Intra-peritoneal (I.P) injection of MO (150 mg/ kg) was started one day after injury and continued once a day for 14 days.

Results

Our results showed motor and sensory functions were improved significantly in the group received a combination of DEX and MO, compared to spinal cord injury group. Mean cavity area was decreased and loss of lower motor neurons and astrogliosis in the ventral horn of spinal cord was significantly prevented in the group received combination of DEX and Melissa officinalis, compared to spinal cord injury group. Furthermore, the findings showed a significant augmentation of electromyography (EMG) recruitment index, increase of myelin diameter, and up-regulation of myelin basic protein in the treated group with combination of DEX and MO.

Conclusion

Results showed that combination of DEX and MO could be considered as a neuroprotective agent in spinal cord injury.

Mechanisms underlying the promotion of functional recovery by deferoxamine after spinal cord injury in rats

Deferoxamine, a clinically safe drug used for treating iron overload, also repairs spinal cord injury although the mechanism for this action remains unknown. Here, we determined whether deferoxamine was therapeutic in a rat model of spinal cord injury and explored potential mechanisms for this effect. Spinal cord injury was induced by impacting the spinal cord at the thoracic T10 vertebra level. One group of injured rats received deferoxamine, a second injured group received saline, and a third group was sham operated. Both 2 days and 2 weeks after spinal cord injury, total iron ion levels and protein expression levels of the proinflammatory cytokines tumor necrosis factor-α and interleukin-1β and the pro-apoptotic protein caspase-3 in the spinal cords of the injured deferoxamine-treated rats were significantly lower than those in the injured saline-treated group. The percentage of the area positive for glial fibrillary acidic protein immunoreactivity and the number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells were also significantly decreased both 2 days and 2 weeks post injury, while the number of NeuN-positive cells and the percentage of the area positive for the oligodendrocyte marker CNPase were increased in the injured deferoxamine-treated rats. At 14–56 days post injury, hind limb motor function in the deferoxamine-treated rats was superior to that in the saline-treated rats. These results suggest that deferoxamine decreases total iron ion, tumor necrosis factor-α, interleukin-1β, and caspase-3 expression levels after spinal cord injury and inhibits apoptosis and glial scar formation to promote motor function recovery.

Genetic Ablation of Soluble TNF Does Not Affect Lesion Size and Functional Recovery after Moderate Spinal Cord Injury in Mice

Traumatic spinal cord injury (SCI) is followed by an instant increase in expression of the microglial-derived proinflammatory cytokine tumor necrosis factor (TNF) within the lesioned cord. TNF exists both as membrane-anchored TNF (mTNF) and as cleaved soluble TNF (solTNF). We previously demonstrated that epidural administration of a dominant-negative inhibitor of solTNF, XPro1595, to the contused spinal cord resulted in changes in Iba1 protein expression in microglia/macrophages, decreased lesion volume, and improved locomotor function. Here, we extend our studies using mice expressing mTNF, but no solTNF (mTNF^Δ/Δ), to study the effect of genetic ablation of solTNF on SCI. We demonstrate that TNF levels were significantly decreased within the lesioned spinal cord 3 days after SCI in mTNF^Δ/Δ mice compared to littermates. This decrease did, however, not translate into significant changes in other pro- and anti-inflammatory cytokines (IL-10, IL-1β, IL-6, IL-5, IL-2, CXCL1, CCL2, or CCL5), despite a tendency towards increased IL-10 and decreased IL-1β, TNFR1, and TNFR2 levels in mTNF^Δ/Δ mice. In addition, microglial and leukocyte infiltration, activation state (Iba1, CD11b, CD11c, CD45, and MHCII), lesion size, and functional outcome after moderate SCI were comparable between genotypes. Collectively, our data demonstrate that genetic ablation of solTNF does not significantly modulate postlesion outcome after SCI.

Plasticity in respiratory motor neurons in response to reduced synaptic inputs: A form of homeostatic plasticity in respiratory control?

For most individuals, the respiratory control system produces a remarkably stable and coordinated motor output-recognizable as a breath-from birth until death. Very little is understood regarding the processes by which the respiratory control system maintains network stability in the presence of changing physiological demands and network properties that occur throughout life. An emerging principle of neuroscience is that neural activity is sensed and adjusted locally to assure that neurons continue to operate in an optimal range, yet to date, it is unknown whether such homeostatic plasticity is a feature of the neurons controlling breathing. Here, we review the evidence that local mechanisms sense and respond to perturbations in respiratory neural activity, with a focus on plasticity in respiratory motor neurons. We discuss whether these forms of plasticity represent homeostatic plasticity in respiratory control. We present new analyses demonstrating that reductions in synaptic inputs to phrenic motor neurons elicit a compensatory enhancement of phrenic inspiratory motor output, a form of plasticity termed inactivity-induced phrenic motor facilitation (iPMF), that is proportional to the magnitude of activity deprivation. Although the physiological role of iPMF is not understood, we hypothesize that it has an important role in protecting the drive to breathe during conditions of prolonged or intermittent reductions in respiratory neural activity, such as following spinal cord injury or during central sleep apnea.

Neutralizing TNFα restores glucocorticoid sensitivity in a mouse model of neutrophilic airway inflammation

Asthma is a heterogeneous disorder, evidenced by distinct types of inflammation resulting in different responsiveness to therapy with glucocorticoids (GCs). Tumor necrosis factor α (TNFα) is involved in asthma pathogenesis, but anti-TNFα therapies have not proven broadly effective. The effects of anti-TNFα treatment on steroid resistance have never been assessed. We investigated the role of TNFα blockade using etanercept in the responsiveness to GCs in two ovalbumin-based mouse models of airway hyperinflammation. The first model is GC sensitive and T helper type 2 (Th2)/eosinophil driven, whereas the second reflects GC-insensitive, Th1/neutrophil-predominant asthma subphenotypes. We found that TNFα blockade restores the therapeutic effects of GCs in the GC-insensitive model. An adoptive transfer indicated that the TNFα-induced GC insensitivity occurs in the non-myeloid compartment. Early during airway hyperinflammation, mice are GC insensitive specifically at the level of thymic stromal lymphopoietin (Tslp) transcriptional repression, and this insensitivity is reverted when TNFα is neutralized. Interestingly, TSLP knockout mice displayed increased inflammation in the GC-insensitive model, suggesting a limited therapeutic application of TSLP-neutralizing antibodies in subsets of patients suffering from Th2-mediated asthma. In conclusion, we demonstrate that TNFα reduces the responsiveness to GCs in a mouse model of neutrophilic airway inflammation. Thus antagonizing TNFα may offer a new strategy for therapeutic intervention in GC-resistant asthma.

Current therapeutic strategies for inflammation following traumatic spinal cord injury

Damage from spinal cord injury occurs in two phases – the trauma of the initial mechanical insult and a secondary injury to nervous tissue spared by the primary insult. Apart from damage sustained as a result of direct trauma to the spinal cord, the post-traumatic inflammatory response contributes significantly to functional motor deficits exacerbated by the secondary injury. Attenuating the detrimental aspects of the inflammatory response is a promising strategy to potentially ameliorate the secondary injury, and promote significant functional recovery. This review details how the inflammatory component of secondary injury to the spinal cord can be treated currently and in the foreseeable future.

Dexamethasone reduces brain cell apoptosis and inhibits inflammatory response in rats with intracerebral hemorrhage

Spontaneous intracerebral hemorrhage (ICH) is associated with high rates of mortality and morbidity. Thus, the identification of novel therapeutic agents for preventing strokes and attenuating poststroke brain damage is crucial. Dexamethasone (DEX) is used clinically to reduce edema formation in patients with spinal cord injury and brain tumors. In this study, we sought to elucidate the effects of DEX treatment on apoptosis and inflammation following ICH in rats. A high dose of DEX (15 mg/kg) was administered immediately following ICH induction and again 3 days later. The inflammatory and apoptotic responses in the rat brains were evaluated by using hematoxylin-eosin, terminal deoxynucleotidyl transferase dUTP nick end labeling, Nissl, and neurofilament-H staining. Levels of phosphorylated neurofilaments and apoptosis-related proteins such as B-cell lymphoma 2 (Bcl-2), Bcl-2 associated X protein (Bax), caspase-3, and P53 were analyzed by Western blotting. This study shows that rats without ICH that received DEX treatment had a fourfold higher expression of Bcl-2 than sham-operated rats. ICH causes an increase in Bax, cleaved caspase-3, and P53 proteins from 4 hr to 7 days following ICH induction. In comparison with the ICH rats, the ICH/DEX rats showed significantly decreased apoptotic cell death and increased neuron survival and maintained neurofilament integrity in the perihematomal region. DEX increased the Bcl-2/Bax ratio and lowered the expression of cleaved caspase-3 at 12 hr and 5 days. The ICH rats were accompanied by activation of the inflammatory response, and DEX treatment modulated the expression of a variety of cell types and then decreased ICH-induced apoptosis.

Effects of an Immunomodulatory Therapy and Chondroitinase After Spinal Cord Hemisection Injury

BACKGROUND:

Individually, immunomodulatory therapy and chondroitinases have demonstrated neuroprotective and potential neuroregenerative effects following spinal cord injury.

OBJECTIVE:

To investigate the therapeutic potential of combined immunomodulatory and chondroitin sulfate-glycosaminoglycan degradation therapy in spinal cord injury.

METHODS:

A combined immunomodulatory treatment using (1) liposome-encapsulated clodronate (selectively depletes peripheral macrophages), and (2) rolipram (a selective type 4 phosphodiesterase inhibitor), along with the chondroitin sulfate proteoglycan-glycosaminoglycan-degrading enzyme, chondroitinase ABC (ChABC), was assessed for its potential to promote axonal regrowth and improve locomotor recovery following midthoracic spinal cord hemisection injury in adult rats.

RESULTS:

We demonstrate that combined treatment with liposomal clodronate, rolipram, and ChABC attenuates macrophage accumulation at the site of injury, reduces axonal die-back of injured dorsal column axons, and produces the greatest improvement in locomotor recovery at 6 weeks postinjury compared with controls and noncombined therapy. Anterograde and retrograde tracing revealed that delivery of clodronate, rolipram, and ChABC did not promote substantial axonal regeneration through the site of injury, although the treatment did limit the extent of axonal die-back. Histological assessments revealed that combined treatment with clodronate/rolipram and/or ChABC resulted in a significant reduction in lesion size and cystic cavitation in comparison with injured controls. Combined clodronate, rolipram, and ChABC treatment reduced the accumulation of macrophages within the injured spinal cord 7 weeks after injury.

CONCLUSION:

The present data suggest that delivery of an immunomodulatory therapy consisting of clodronate and rolipram, in combination with ChABC, reduces axonal injury and enhances neuroprotection, plasticity, and hindlimb functional recovery after hemisection spinal cord injury in adult rats.

Effects of the combination of methylprednisolone with aminoguanidine on functional recovery in rats following spinal cord injury

Methylprednisolone (MP), a synthetic glucocorticoid, has been widely used as a standard therapeutic agent for the treatment of spinal cord injury (SCI). The combination of MP and other pharmacological agents aimed at enhancing functional recovery is desirable as the beneficial effects of MP are controversial, due to a variety of side-effects. Aminoguanidine (AG), a small water-soluble compound, is potentially useful in the treatment of acute SCI. The aim of the present study was to determine the effects of MP and AG, administered in combination, following SCI in adult rats. In rats with SCI, the combination therapy group treated with AG (75 mg/kg) and MP (0.75 mg/kg) exhibited significantly reduced levels of cytokine expression and cell apoptosis compared with those in the control group. In addition, the data demonstrated that the combination therapy significantly enhanced the recovery of limb function. These data clearly suggest that treatment with a combination of MP and AG represents a promising strategy of clinically applicable pharmacological therapy for the rapid initiation of neuroprotection following SCI.

Combination therapy with melatonin and dexamethasone in a mouse model of traumatic brain injury

Traumatic brain injury (TBI) is a major cause of preventable death and morbidity in young adults. This complex condition is characterized by a significant blood-brain barrier leakage that stems from cerebral ischemia, inflammation, and redox imbalances in the traumatic penumbra of the injured brain. Recovery of function after TBI is partly through neuronal plasticity. In order to test whether combination therapy with melatonin and dexamethasone (DEX) might improve functional recovery, a controlled cortical impact (CCI) was performed in adult mice, acting as a model of TBI. Once trauma has occurred, combating these exacerbations is the keystone of an effective TBI therapy. The therapy with melatonin (10  mg/kg) and DEX (0.025  mg/kg) is able to reduce edema and brain infractions as evidenced by decreased 2,3,5-triphenyltetrazolium chloride staining across the brain sections. Melatonin- and DEX-mediated improvements in tissue histology shown by the reduction in lesion size and an improvement in apoptosis level further support the efficacy of combination therapy. The combination therapy also blocked the infiltration of astrocytes and reduced CCI-mediated oxidative stress. In addition, we have also clearly demonstrated that the combination therapy significantly ameliorated neurological scores. Taken together, our results clearly indicate that combination therapy with melatonin and DEX presents beneficial synergistic effects, and we consider it an avenue for further development of novel combination therapeutic agents in the treatment of TBI that are more effective than a single effector molecule.

Late blocking of peripheral TNF-α is ineffective after spinal cord injury in mice

Spinal cord injury (SCI) is characterized by different phases of inflammatory responses. Increasing evidence indicates that the early chronic phase (two to three weeks after SCI) is characterized by a dramatic invasion of immune cells and a peak of pro-inflammatory cytokine levels, such as tumor necrosis factor-α (TNF-α) derived from the injured spinal cord as well as from injured skin, muscles and bones. However, there is substantial controversy whether these inflammatory processes in later phases lead to pro-regenerative or detrimental effects. In the present study, we investigated whether the inhibition of peripheral TNF-α in the early chronic phase after injury promotes functional recovery in a dorsal hemisection model of SCI. Three different approaches were used to continuously block peripheral TNF-α in vivo, starting 14 days after injury. We administered the TNF-α blocker etanercept intraperitoneally (every second day or daily) as well as continuously via osmotic minipumps. None of these administration routes for the TNF-α inhibitor influenced locomotor restoration as assessed by the Basso mouse scale (BMS), nor did they affect coordination and strength as evaluated by the Rotarod test. These data suggest that peripheral TNF-α inhibition may not be an effective therapeutic strategy in the early chronic phase after SCI.

Etanercept treatment enhances clinical and neuroelectrophysiological recovery in partial spinal cord injury

PURPOSE

To investigate the effect of an anti-TNF-α agent (etanercept) on recovery processes in a partial spinal cord injury (SCI) model using clinical and electrophysiological tests.

METHODS

Twenty-four New Zealand rabbits were divided into three groups: group 1 [SCI + 2 ml saline intramuscular (i.m.), n = 8], group 2 (SCI + 2.5 mg/kg etanercept, i.m., 2-4 h after SCI, n = 8) and group 3 (SCI + 2.5 mg/kg etanercept, i.m., 12-24 h after SCI, n = 8). Rabbits were evaluated before SCI, immediately after SCI, 1 week after, and 2 weeks after SCI, clinically by Tarlov scale and electrophysiologically by SEP.

RESULTS

Tarlov scores of groups 2 and 3 were significantly better than group 1, 2 weeks after SCI. SEP recovery was significantly better in groups 2 and 3 than group 1, 2 weeks after SCI.

CONCLUSIONS

These results show that blocking TNF-α mediated inflammation pathway by an anti-TNF-α agent enhances clinical and electrophysiological recovery processes in partial SCI model.

Evaluation of the effects of hyperbaric oxygen therapy for spinal cord lesion in correlation with the moment of intervention

STUDY DESIGN

Experimental, controlled, animal study.

OBJECTIVES

To evaluate the functional effect of hyperbaric oxygen therapy administered shortly, one day after, and no intervention (control) in standardized experimental spinal cord lesions in Wistar rats.

SETTING

São Paulo, Brazil.

METHODS

In all, 30 Wistar rats with spinal cord lesions were divided into three groups: one group was submitted to hyperbaric oxygen therapy beginning half an hour after the lesion and with a total of 10 one-hour sessions, one session per day, at 2 atm; the second received the same treatment, but beginning on the day after the lesion; and the third received no treatment (control). The Basso, Beattie and Bresnahan scales were used for functional evaluation on the second day after the lesion and then weekly, until being killed 1 month later.

RESULTS

There were no significant differences between the groups in the functional analysis on the second day after the lesion. There was no functional difference comparing Groups 1 and 2 (treated shortly after or one day after) in any evaluation moment. On the 7th day, as well as on the 21st and 28th postoperative days, the evaluation showed that groups 1 and 2 performed significantly better than the control group (receiving no therapy).

CONCLUSION

Hyperbaric chamber therapy is beneficial in the functional recovery of spinal cord lesions in rats, if it is first administered just after spinal cord injury or within 24 h.

Tumor necrosis factor-α antagonist reduces apoptosis of neurons and oligodendroglia in rat spinal cord injury

STUDY DESIGN

To examine the effects of a tumor necrosis factor (TNF)-α antagonist (etanercept) on rat spinal cord injury and identify a possible mechanism for its action.

OBJECTIVE

To elucidate the contribution of etanercept to the pathologic cascade in spinal cord injury and its possible suppression of neuronal and oligodendroglial apoptosis.

SUMMARY OF BACKGROUND DATA

Etanercept has been recently used successfully for treatment of inflammatory disorders. However, only a few studies have examined its role in suppressing neuronal and oligodendroglial apoptosis in spinal cord injury.

METHODS

Etanercept or saline (control) was administered by intraperitoneal injection 1 hour after thoracic spinal cord injury in rats. The expressions and localizations of TNF-α, TNF receptor 1 (TNFR1), and TNF receptor 2 (TNFR2) were examined by immunoblot and immunohistochemical analyses. Spinal cord tissue damage between saline- and etanercept-treated groups was also compared after hematoxylin-eosin and luxol fast blue (LFB) staining. The Basso-Beattie-Bresnahan (BBB) scale was used to evaluate rat locomotor function after etanercept administration. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells were counted and the immunoreactivity to active caspase-3 and caspase-8 was examined after etanercept administration.

RESULTS

Immunoblot and double immunofluorescence staining revealed suppression of TNF-α, TNFR1, and TNFR2 expression after administration of etanercept in the acute phase of spinal cord injury. LFB staining demonstrated potential myelination in the etanercept-treated group from 2 week after spinal cord injury, together with an increased BBB locomotor score. Double immunofluorescence staining showed a significant decrease in TUNEL-positive neurons and oligodendroglia from 12 hour to 1 week in the gray and white matters after etanercept administration. Immunoblot analysis demonstrated overexpression of activated caspase-3 and caspase-8 after spinal cord injury, which was markedly inhibited by etanercept.

CONCLUSION

Our results indicated that etanercept reduces the associated tissue damage of spinal cord injury, improves hindlimb locomotor function, and facilitates myelin regeneration. This positive effect of etanercept on spinal cord injury is probably attributable to the suppression of TNF-α, TNFR1, TNFR2, and activated caspase-3 and caspase-8 overexpressions, and the inhibition of neuronal and oligodendroglial apoptosis.

Anti-TNF therapy in the injured spinal cord

Spinal cord injury (SCI) has a significant impact on the quality and expectancy of life. It also carries a heavy economic burden, with considerable costs associated with primary care and loss of income. The normal architecture of the spinal cord is radically disrupted by injury. After the initial insult, structure and function are lost through active secondary processes that involve reactive astrocytes, glial progenitors, microglia, macrophages, fibroblasts and Schwann cells. These cells produce chemokines and cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β, which mediate the recruitment of inflammatory cells to the injury site. Targeting of these cytokines represents a potential strategy to reduce the secondary damage in SCI. In this review, we focus on several emerging strategies to neutralize TNF-α, including antibodies, soluble receptors, recombinant TNF-binding proteins, TNF receptor fusion proteins, and non-specific agents (e.g. thalidomide) and discuss their potential as therapy for SCI.

The LTB4-BLT1 axis mediates neutrophil infiltration and secondary injury in experimental spinal cord injury

Traumatic injury in the central nervous system induces inflammation; however, the role of this inflammation is controversial. Precise analysis of the inflammatory cells is important to gain a better understanding of the inflammatory machinery in response to neural injury. Here, we demonstrated that leukotriene B4 plays a significant role in mediating leukocyte infiltration after spinal cord injury. Using flow cytometry, we revealed that neutrophil and monocyte/macrophage infiltration peaked 12 hours after injury and was significantly suppressed in leukotriene B4 receptor 1 knockout mice. Similar findings were observed in mice treated with a leukotriene B4 receptor antagonist. Further, by isolating each inflammatory cell subset with a cell sorter, and performing quantitative reverse transcription-PCR, we demonstrated the individual contributions of more highly expressed subsets, ie, interleukins 6 and 1beta, tumor necrosis factor-alpha, and FasL, to the inflammatory reaction and neural apoptosis. Inhibition of leukotriene B4 suppressed leukocyte infiltration after injury, thereby attenuating the inflammatory reaction, sparing the white matter, and reducing neural apoptosis, as well as inducing better functional recovery. These findings are the first to demonstrate that leukotriene B4 is involved in the pathogenesis of spinal cord injury through the amplification of leukocyte infiltration, and provide a potential therapeutic strategy for traumatic spinal cord injury.

The P2Y-like receptor GPR17 as a sensor of damage and a new potential target in spinal cord injury

Upon central nervous system injury, the extracellular concentrations of nucleotides and cysteinyl-leukotrienes, two unrelated families of endogenous signalling molecules, are markedly increased at the site of damage, suggesting that they may act as 'danger signals' to alert responses to tissue damage and start repair. Here we show that, in non-injured spinal cord parenchyma, GPR17, a P2Y-like receptor responding to both uracil nucleotides (e.g. UDP-glucose) and cysteinyl-leukotrienes (e.g. LTD4 and LTC4), is present on a subset of neurons and of oligodendrocytes at different stages of maturation, whereas it is not expressed by astrocytes. GPR17 immunoreactivity was also found on ependymal cells lining the central canal that still retain some of the characteristics of stem/progenitor cells during adulthood. Induction of spinal cord injury (SCI) by acute compression resulted in marked cell death of GPR17+ neurons and oligodendrocytes inside the lesion followed by the appearance of proliferating GPR17+ microglia/macrophages migrating to and infiltrating into the lesioned area. Moreover, 72 h after SCI, GPR17+ ependymal cells started to proliferate and to express GFAP, suggesting their activation and 'de-differentiation' to pluripotent progenitor cells. The in vivo knock down of GPR17 by an antisense oligonucleotide strategy during SCI induction markedly reduced tissue damage and related histological and motor deficits, thus confirming the crucial role played by this receptor in the early phases of tissue damage development. Taken together, our findings suggest a dual and spatiotemporal-dependent role for GPR17 in SCI. At very early times after injury, GPR17 mediates neuronal and oligodendrocyte death inside the lesioned area. At later times, GPR17+ microglia/macrophages are recruited from distal parenchymal areas and move toward the lesioned zone, to suggest a role in orchestrating local remodelling responses. At the same time, the induction of the stem cell marker GFAP in GPR17+ ependymal cells suggests initiation of repair mechanisms. Thus, GPR17 may act as a 'sensor' of damage that is activated by nucleotides and cysteinyl-leukotrienes released in the lesioned area, and could also participate in post-injury responses. Moreover, its presence on spinal cord pre-oligodendrocytes and precursor-like cells suggests GPR17 as a novel target for therapeutic manipulation to foster remyelination and functional repair in SCI.

Acute rolipram/thalidomide treatment improves tissue sparing and locomotion after experimental spinal cord injury

Traumatic spinal cord injury (SCI) causes severe and permanent functional deficits due to the primary mechanical insult followed by secondary tissue degeneration. The cascade of secondary degenerative events constitutes a range of therapeutic targets which, if successfully treated, could significantly ameliorate functional loss after traumatic SCI. During the early hours after injury, potent pro-inflammatory cytokines, including tumor necrosis factor alpha (TNF-alpha) and interleukin-1 beta (IL-1beta) are synthesized and released, playing key roles in secondary tissue degeneration. In the present investigation, the ability of rolipram and thalidomide (FDA approved drugs) to reduce secondary tissue degeneration and improve motor function was assessed in an experimental model of spinal cord contusion injury. The combined acute single intraperitoneal administration of both drugs attenuated TNF-alpha and IL-1beta production and improved white matter sparing at the lesion epicenter. This was accompanied by a significant (2.6 point) improvement in the BBB locomotor score by 6 weeks. There is, at present, no widely accepted intervention strategy that is appropriate for the early treatment of human SCI. The present data suggest that clinical trials for the acute combined application of rolipram and thalidomide may be warranted. The use of such "established drugs" could facilitate the early initiation of trials.

Blood-spinal cord barrier permeability in experimental spinal cord injury: dynamic contrast-enhanced MRI

After a primary traumatic injury, spinal cord tissue undergoes a series of pathobiological changes, including compromised blood-spinal cord barrier (BSCB) integrity. These vascular changes occur over both time and space. In an experimental model of spinal cord injury (SCI), longitudinal dynamic contrast-enhanced MRI (DCE-MRI) studies were performed up to 56 days after SCI to quantify spatial and temporal changes in the BSCB permeability in tissue that did not show any visible enhancement on the post-contrast MRI (non-enhancing tissue). DCE-MRI data were analyzed using a two-compartment pharmacokinetic model. These studies demonstrate gradual restoration of BSCB with post-SCI time. However, on the basis of DCE-MRI, and confirmed by immunohistochemistry, the BSCB remained compromised even at 56 days after SCI. In addition, open-field locomotion was evaluated using the 21-point Basso-Beattie-Bresnahan scale. A significant correlation between decreased BSCB permeability and improved locomotor recovery was observed.